Pulmonary macrophages defend the respiratory surfaces of the lungs against deposited particles through their phagoctic and migratory capabilities. a novel method, involving microscopic magnetic particles, promises to be a valuable expermental indicator of macrophage function, by providing information noninvasively on the motions of cell organelles. When humans or animals inhale a magnetic-particle aerosol, a fraction of the particles are retained in the lungs and ingested by pulmonary macrophages. We have found that for phagocytized particles, cytoplasmic motions rotate the particles and produce detectable changes in the magnetic field. Thus, sensitive magnetometry may serve as an experimental probe of the motile status of macrophages, specifically, a probe not rrequiring optical observation of cells on the stage of a microscope. In addition, intracellular particles can be twisted by an applied external field, which allows measurement of cytosol viscoelasticity. The proposed research will examine magnetometric phenomena for lung macrophages in culture. We week to answer the following question: (1) How do magnetometric signals correlate to optically-observed cell organelle motions? (2) How do magnetometrically-measured motion and viscoelasticity change with macrophage functional status and cytoskeletal integrity? (3) Can intracellular magnetic particle motions be used to help formulate and test models of intracellular force generation and viscoelasticity? The goal is to critically examine magnetometry as a non-optical method for probing cellular motile proceses. Magnetometry may provide a unique diagnostic procedure for in situ assessment of the behavior of phagocvytic cells.